DORSAL VERTEBRiE. 29 



over the whole length of the chest. Their bodies, the smallest 

 of the true vertebras, are short, thick, and somewhat semicircular 

 in form, each presenting a middle ridge along its under surface, 

 to which the inferior common ligament is attached. The superior 

 surface of the body, which forms the floor of the spinal canal, is 

 flattened and quadrilateral, presenting longitudinal furrows for 

 the spinal vessels, and often a central tranverse one, partially 

 covered by a bony plate. The anterior extremity presents a 

 slightly convex head, on the superior and lateral aspect of which 

 is a semicircular depression corresponding with another on the 

 posterior extremity of the vertebra in front, so that together they 

 form a cup-shaped cavity for the articulation of a rib, each articu- 

 lating with one-half of the head of the rib. The posterior 

 extremity is concave, to articulate with the contiguous bone, and 

 has on each side an articular depression similar to those on the 

 anterior extremit3\ The tranverse i^rocesses, rising from the 

 sides of the arches, are small ; superiorly and anteriorly they are 

 roughened for muscular attachment, and at its postero -inferior 

 part, each presents a flat, smooth facet which articulates with the 

 tubercle of the next anterior rib. 



The neural spines, larger than in any other region, vary much 

 in size, shape, and direction, the first twelve being directed back- 

 wards, the next three nearly upright, and the last three forwards ; 

 their length gradually increases to the fifth, which is usually the 

 longest, and then decreases to the fourteenth, which is generally 

 somewhat shorter than those behind it ; the first is small and 

 sharp, and the second, which is abruptly bent backwards, is very 

 strong ; the summits of the next six or seven are flattened, 

 roughened, and expanded laterally, assuming a bifid appearance, 

 giving greater surface for the attachment of muscles and the great 

 suspensory ligament of the head and neck, the ligamentum 

 nuclice. The lateral surfaces are convex and slightly roughened, 

 the anterior borders being thin and serrated, while the posterior, 

 of the higher spines especially, are broad and concave, becoming 

 cleft as they approach the oblique processes. 



The oblique processes are small, and their facets are more 

 horizontal than in the cervical region, and close together. The 

 pedicles are short and strong, and, with the exception of the 

 anterior four or five, possess notches on their posterior edges 

 only ; backwards, we find these notches become more and more 

 closed in, until posteriorly there are foramina in lieu of notches. 



